1. Field of the Invention
The present invention relates to a cleaning device including an elastic blade for use in an image forming apparatus into which an electrophotographic process is adopted, and an image forming apparatus and a process cartridge on which the cleaning device is mounted.
2. Related Background Art
Conventionally from a viewpoint of a simple constitution and a reasonable price as a cleaning means included in an image forming apparatus into which an electrophotographic process is adopted, there has been prevalently used what is called a blade cleaning method with an elastic blade as shown in FIG. 10. In FIG. 10, a photosensitive drum 101 is used as an image bearing member driven to rotate in a direction indicated by an arrow, and a cleaning means 102 comprises a waste toner collecting container 103, a supporting member 104 attached to the waste toner collecting container 103, an elastic blade 105 supported by the supporting member 104, and a toner scavenging sheet 106. The elastic blade 105, which is made of urethane rubber, abuts against a surface of the photosensitive drum 101 what is called in the counter direction. In other words, at least a distal end of the elastic blade 105 supported by the supporting member 104 abuts against the surface of the photosensitive drum 101 and at least a part of the abutment surface of the elastic blade 105 against the surface of the photosensitive drum 101 is gradually spaced from the surface of the photosensitive drum 101 in a downstream direction of a rotary direction of the photosensitive drum 101.
As a demand for color image forming apparatuses is increased in recent years, however, more stable toner is required, and therefore there is a tendency to adopt almost spherical toner capable of having more uniform charging characteristics as an expedient.
On the other hand, it is known that this type of substantially spherical toner is very hard to be removed by being scraped off from the surface of the photosensitive drum 101 by the elastic blade 105 as cleaning means. It is deemed to be why the elastic blade 105 abutting against the surface of the photosensitive drum 101 chatters when the photosensitive drum 101 is driven to rotate and the substantially spherical toner easily passes through a slight gap between the surface of the photosensitive drum 101 and the elastic blade 105 generated at that time.
Additionally, in general, toner has on its outer surface additive particles each having smaller particle diameter than that of the toner for the main purpose of stabilizing toner by increasing its charges. As the outer additive, powder of the silica group or the like is used, for example, and it is attached on the surface of each toner particle as if each toner particle is sprinkled with the powder.
In the substantially spherical toner, however, an adhesive force between the toner and its outer additive tends to be smaller than that between aspherical toner and its outer additive. If this type of toner is used for forming an image, the outer additive is easily liberated from the surface of respective toner particles gradually as the number of the images formed sheets is increased.
In addition, since the outer additive made of particles each having a smaller particle diameter in comparison with the toner as described above, the elastic blade 105 abutting against the surface of the photosensitive drum 101 chatters when the photosensitive drum 101 is driven to rotate, and therefore there is a tendency that the additive is relatively easy to pass through a slight gap between the surface of the photosensitive drum 101 and the elastic blade 105 generated at that time.
To solve this problem, in an image forming apparatus for performing an image forming operation by using almost spherical toner, there is disclosed means for preventing a cleaning failure when removing transfer residual toner on the surface of the photosensitive drum 101 after a transfer process and its outer additive from the surface of the photosensitive drum by causing the elastic blade 105 to abut against the surface of the image bearing member 101 at an abutment pressure with a linear load of 55 gf/cm or greater and 105 gf/cm or smaller (Japanese Patent Application Laid-Open No. 10214013).
The greater the abutment pressure of the elastic blade 105 against the photosensitive drum 101 is, however, there more easily occurs an undesirable phenomenon called xe2x80x9cfusion bondxe2x80x9d in which outer additive or the like is fixed on the surface of the photosensitive drum 101 caused by the outer additive passing through the abutment portion between the photosensitive drum 101 and the elastic blade 105.
It is an object of the present invention to provide an image forming apparatus in which charging means, exposure means, developing means, and transfer means are arranged in this order around a rotatable image bearing member, for visualizing an electrostatic latent image formed on a surface of the image bearing member by substantially spherical toner, electrostatically transferring it onto a surface to be transferred in a transfer position, and preventing a cleaning failure by using a cleaning device mounted for a purpose of removing residual substantially spherical toner remaining on the surface of the image bearing member from the surface of the image bearing member so as to suppress a fusion bond of toner and outer additive onto the image bearing member.
It is another object of the present invention to provide a cleaning device according to the above for suppressing an inroad amount xcex4 to the image bearing member of an elastic blade required for causing the elastic blade to abut against the image bearing member at a high abutment pressure to prevent the elastic blade from abutting against the image bearing member at a portion other than the edge (side abutment) of the elastic blade which may occur at an extreme increase of the inroad amount xcex4, so as to prevent a cleaning failure.
It is still another object of the present invention to provide a cleaning device according to the above in which it is hard to generate a gap between the surface of the image bearing member and the elastic blade when the elastic blade abutting against the surface of the image bearing member chatters thereby the substantially spherical toner and the outer additive are prevented from passing through the gap in order to enhance its cleaning property.
It is a further object of the present invention to provide an image forming apparatus for forming an image by using substantially spherical toner in which a cleaning failure is prevented to suppress a fusion bond of the toner and its outer additive onto an image bearing member so as to obtain a high-quality output image for a long period.
It is a still further object of the present invention to provide an image forming apparatus in which a part of a mechanism required for forming an image is integrated with being detachably mountable to a main body of the image forming apparatus, including at least an image bearing member and the above cleaning device, in order to facilitate maintenance of the image forming apparatus and replacement of consumable components.
According to one aspect, the present invention which achieves these objects relates to a cleaning member for use in a cleaning device applied to an electrophotographic apparatus comprising an elastic blade which has a value of 200 kgf/cm2 or greater or breaks a tensile strength of 300% elongation to rub and remove toner having a shape coefficient SF1 of 100 to 150 remaining in a cleaned member in a main body of the electrophotographic apparatus and a blade supporting member for supporting this elastic blade.
According to another aspect, the present invention which achieves these objects relates to a cleaning device to which the cleaning member is applied, an image forming apparatus having this cleaning device, or a process cartridge detachably mountable to a main body of the image forming apparatus.